Saliency Measure

We can assign a saliency measure for an edge (called edge saliency) depending on how likely a salient closed contour passes through that edge. A salient closed contour is one that conforms to the principles of proximity and smooth-continuation. Smooth-continuity of a curve between two edges implies that the tangent at any point along the curve is continuous. Such tangent-continuity for curves passing between a pair of edges is modeled by the smooth motion of the particle going from one edge to the other. However, what we are really interested in are global contours that thread through many edges. Smoother contours are judged to be more salient. Since tangent-continuity between successive edges of the contour are imposed by the smooth motion of the particle as described above, what remains is the imposition of tangent-continuity at the edges themselves. This is done through the use of directed edges. A given edge in the image has a given orientation. A particle can arrive or leave at the edge in either one of two directions along the edge. To impose tangent-continuity at the edges, we need the particle to arrive and leave an edge in the same direction. Hence we replace each oriented edge with two directed edges, one of the directions along the original orientation of the edge and the other along the opposite direction.

	Saliency plots for the two-pear example with directed edges. As mentioned before directed edges are used to impose smoothness of contours at the edges. The length of each edge is proportional to its saliency.
	Saliency plots for the two-pear example with undirected edges. The measure completely misses the contours bounding the two pears.

Shyjan Mahamud

Last modified: Tue Sep 8 18:45:30 EDT 1998